1. Field of the Invention
The present invention relates to a gas sensor including a plate-like gas sensor element.
2. Description of the Related Art
As a gas sensor that carries out detection and measurement of the concentration of a specified gas component contained in an exhaust gas of an internal-combustion engine or the like, one including a plate-type gas sensor wherein a plurality of substrates are stacked one on another has heretofore been known. The gas sensor element has a sensing portion provided in a leading end portion thereof, and carries out a detection and measurement of the concentration of a specified gas component by exposing the sensing portion to an exhaust gas. Also, in this kind of gas sensor, electrode pads for outputting a detection signal from the sensing portion to an external circuit are disposed on a surface in a rear end portion of the gas sensor element. Furthermore, a technology is known wherein a ridge line (between a surface of the gas sensor element on which the electrode pads are provided and a side surface perpendicular to the surface) is chamfered and ground, thereby eliminating a surface defect, such as a burr formed at the ridge line when manufacturing the element. This measure can suppress damage such as a crack or chipping caused by a shock from outside the gas sensor element. For example, in JP-A-2004-251654, a chamfered portion is provided by chamfering a ridge line, provided in a longitudinal direction of a gas sensor element, uniformly at a chamfer angle of 45°.
A chamfer angle and chamfer amount are specified for the chamfered portion from the standpoint of imparting thermal shock resistance to a leading end portion of the gas sensor element exposed to an exhaust gas. Further, a chamfered portion uniform in the longitudinal direction of the gas sensor element, also including a rear end portion of the gas sensor element, is provided.
However, when this kind of chamfered portion is provided in a gas sensor element on a surface of which a plurality of electrode pads are disposed, the area of the surface (the width of the surface) in the rear end portion on which the electrode pads are disposed is reduced. This makes it necessary to further shorten the distances between the electrode pads. Because of this, there is a danger of bringing about a decrease in the insulating performance between the electrode pads. On the other hand, when the distances between the electrode pads are secured by reducing the area of the electrode pads in order to secure the insulating performance between the electrode pads, there is a danger that the contactability between the electrode pads and connection terminals decreases.